1. Field of the Invention
The present invention relates to an enlarger for making photographic prints from original films.
2. Description of the Prior Art
A number of procedures are required in making a photographic print from an original film. By way of example, prior to the exposure procedure being performed, a focusing procedure has to be performed to focus an image of the original film on a surface where a photographic paper is placed. In addition, where a color print is desired to be made from an original color film, the color of a light source has to be adjusted so that the ultimate color print can exhibit a desired tone of color. For this adjustment, means is provided for analyzing the color of the light from the light source that has passed through the color film.
A prior art color enlarger is so designed that the color of the light from the light source can be adjusted to change in a desired direction. However, even if the color of the light from the light source has been adjusted to change in the same direction, the tone of color in the resultant color print may change in the reverse direction depending on whether the type of the original color film is a negative one or whether it is a positive one. Accordingly, the user of the enlarger must take note of the type of the original color film when adjusting the color of the light from the light source so that the desired change in tone of the color print can be realized. This is hard work for most amateur photographers to do, and even a experienced photographer often fails to do the adjustment properly.
Moreover, even during the focusing operation and the color analysis both to be performed prior to the actual print making, procedures are complicated and time-consuming and, therefore, improvement in manipulativity has long been desired.
It is to be noted that for the focusing operation to be performed, the use of a light source for a focusing operation is required. According to the prior art, the use of a flash light source as the light source for an exposure operation upon printing is well known. However, since the light to be used during the focusing procedure must be a continuous one, a separate focusing light source capable of emitting a continuous light is provided in addition to the flash light source, rendering the enlarger itself to be bulky and expensive.
For the color analysis to be performed, on the other hand, the use of an optical measuring instrument for measuring the light that has passed through the color original film is required. In general the optical measuring instrument makes use of a flash light source capable of emitting a predetermined amount of light. Considering the fact that the quantity of light reflected on or transmitted through the object and then incident on the optical measuring instrument varies within a wide range depending on the nature of a target object the optical measuring instrument has to be provided with a light measuring circuit exactly responsive to a change in incident light quantity within an extremely wide range. However, the design of the light measuring circuit is limited because it is difficult to manufacture a light measuring circuit capable of responding to light varying in such a wide range.
One way contemplated to expand the coverage of measurement of the optical measuring instrument would be to make the optical measuring instrument have a capability of being switched between a mode in which it responds to a relatively large amount of light and another mode in which it responds to a relativley small amount of light, so that the optical measuring instrument can be used in one of these modes depending on the amount of light to be measured. According to this way, however, it has been found that the measuring circuit in the optical measuring instrument tends to become bulky and complicated.